A1 Refereed original research article in a scientific journal
Finding graph embeddings by incremental low-rank semidefinite programming
Authors: Seppo Pulkkinen
Publisher: Taylor & Francis
Publication year: 2015
Journal: Optimization Methods and Software
Volume: 30
Issue: 5
First page : 1050
Last page: 1076
Number of pages: 27
ISSN: 1055-6788
DOI: https://doi.org/10.1080/10556788.2015.1014553
Finding a low-dimensional embedding of a graph of n nodes in Rd is an essential task in many applications.
For instance, maximum variance unfolding (MVU) is a well-known dimensionality reduction
method that involves solving this problem. The standard approach is to formulate the embedding problem
as a semidefinite program (SDP). However, the SDP approach does not scale well to large graphs. In
this paper, we exploit the fact that many graphs have an intrinsically low dimension, and thus the optimal
matrix resulting from the solution of the SDP has a low rank. This observation leads to a quadratic
reformulation of the SDP that has far fewer variables, but on the other hand, is a difficult convex maximization
problem. We propose an approach for obtaining a solution to the SDP by solving a sequence
of smaller quadratic problems with increasing dimension. Utilizing an augmented Lagrangian and an
interior-point method for solving the quadratic problems, we demonstrate with numerical experiments on
MVU problems that the proposed approach scales well to very large graphs.